Prior to commencing comprehensive image data processing, which may include searching for symbol or character representations, decoding and character recognition processing, presently available optical readers clock out and capture in a memory location at least one exposure test frame of image data, read pixel data from the memory-stored exposure test frame to determine an exposure parameter value that is based on actual illumination conditions, then utilize the exposure parameter value in the exposure of a frame of image data that is clocked out, and then subjected to searching, decoding, and/or character recognition processing. The frame of image data exposed utilizing the exposure parameter based on acutal illumination conditions is not available for reading until after it is clocked out. Presently available optical readers therefore exhibit an appreciable inherent exposure parameter determination delay. Readers having higher resolution imagers have slower frame clock out rates and therefore longer exposure parameter determination delays.
There is a growing demand for higher resolution optical readers, including optical readers that incorporate mega pixel image sensors. Accordingly, there is growing need to address the parameter determination delay problem associated with presently available optical readers.